5 Answers
5

that is my point of view too, but the guy on the store told me it was balanced so I thought that maybe the cable would duplicate the mono signal from the TS connector, and invert one of the signals sending them to the pins of XLR through a 3 wired cable replicating the effect of noise cancellation of balanced cables. but I doubt this is possible to do with just one cable (I'm just a newbie in this area). I think I will go back to the store tomorrow to change the cable. thanks for your answer
– andrespJul 25 '11 at 21:46

@andresp - the only way it could be balanced with a tip/sleeve is if it had some electronics built into the plug/cable, which would make the cable more complicated and more expensive to build. that would would only provide a balanced signal over the cable, not at the adapter. of course, it would also need a power source as well. doing that passively would mess with the phase of the signal over the two conductors, rendering any balancing that might have existd pointless. a cable manufacturer would never do this.
– Shaun FarleyJul 25 '11 at 22:26

thanks MGriggs, I had already checked that site before, the only doubt that remained after seeing it that made me post this question was the introduction "The most comon way to wire...". It only talks about the most common way...
– andrespJul 25 '11 at 21:49

I just thought I would go into more detail about what Balanced and Unbalanced means for you.

This is a balanced 1/4" connection (TRS)
Notice the two black lines. The first section of metal is the sleeve (left side of picture), then between the lines is the ring, and finally the point is called the tip. These are three separate signal paths.

Here is an unbalanced 1/4" connection (TS) on top. (The bottom is a 3.5mm connection)
Notice the ring is not there anymore.

Now, about balance. Cables will pick up noise (like radio frequencies) along their length similar to antennas. On the TRS, the Tip and Ring carry audio signals, flipped out of phase (meaning they cancel each other out, resulting in silence). Then when the signal reaches the end, the hardware you are plugging into will flip one (not sure which) back into phase. So when the signal is flipped, all the noise picked up cancels itself out, and the audio sounds clean.

TS is unbalanced. You might think that it would work to use a balanced cable between them and connect (from XLR to TS) shield to S, hot to T, cold to S and thus get the benefits of a balanced connection.

However, part of the deal of a balanced connection is that hot and cold signal are used differentially and are subject to the same electrical conditions. This includes the same terminating impedance at the end of the line in order to have equal effect of disturbances on both signal lines. A "cheap man's balancer" would therefore at least require a resistor in the cold signal line matching the input impedance in the hot line.

However, for such a "cheap balancer" to be fully effective, the signal source needs to be not just differential but balanced (easy when it's just a "floating" sensor like with a dynamic microphone, but if active electronics are involved, there is more effort involved).

Also it is rather hard to get impressive "common mode rejection" values just by matching independent resistances.

So getting back to the original question: a TS-to-XLR cable not especially touting a "built-in DI" (which would be a small transformer near the TS end) will be using an unbalanced cable. Using a balanced cable would not really improve matters and make the cable more expensive.

The proof is in the pudding, though: is a photograph of such an adapter cable opened. There are just two connections, one being the shield in an isolating piece of tube. You can see the shield being soldered to two terminals (the connecting copper from middle to lower terminal is a bit hard to see on the photograph).